What applies to security certificates for the www and non-www form of a domain name?

Issuing authorities apply different rules as to whether a certificate can be used for the www-form or the non-www form of the domain name for which they are issued. Next we will see what applies per issuing authority, but also per certificate category.

TopHost's 3 main certificate categories are Standard, Wildcard and SAN Certificates:

1. Standard: provide protection for a domain name.
2. Wildcard: provide protection for the subdomains of a top-level domain.
3. SAN: can be used to protect multiple Fully Qualified Domain Names with different root names.

Geotrust

- Standard: if SSL is issued for www.domain.com, domain.com is also covered.
- Wildcard: *.domain.com covers domain.com and www.domain.com
- SAN: if www.domain.com is added to SSL as one of the central domains, domain.com is also covered for free

Symantec

- Standard: certificates cover both formats.
- Wildcard: the format *.domain.com covers the root domain.com
- SAN: www.domain.com does not cover the non-www format. The two domains should be added separately.
certificates cover both formats.

If you are interested in using the certificate for both formats, choose a certificate from another issuing authority that meets this requirement.

Thawte

- Standard: certificates only cover www.domain.com or non-www "domain.com". Not both.
- Wildcard: *.domain.com does not cover the root domain.com
- SAN: www.domain.com does not cover the non-www format. The two domains should be added separately.

If you are interested in using the certificate for both formats, choose a certificate from another issuing authority that meets this requirement.

Note: You can still enable a 301 redirect so that it redirects at no extra cost.
Trustwave

- Standard: Premium SSL & Premium EV SSL cover by default both the www and the non-www format, regardless of which of the two will be declared during the installation of the certificate.
- Wildcard: cover the root format if applicable (applies to recent TrustWave certificate purchases - article date: 02/05/2014)

Comodo

Standard: if SSL is issued for www.domain.com, domain.com is also covered.
Wildcard: *.domain.com covers domain.com and www.domain.com